What's the difference between DDR3 and DDR4?

[Cruxell]

Please give a comprehensive explanation.

 

[Seanie280672]

Please give a comprehensive explanation.

Here: http://www.pcgamer.com/the-differences-between-ddr3-and-ddr4-ram/

 

[raisonjohn]

Please give a comprehensive explanation.

Illustrations/visuals would better describe the differences:

Source: https://www.itechtics.com/ddr3-vs-ddr4-comparison/

Source: http://www.eetimes.com/document.asp?doc_id=1280577

Source: https://www.howtoseeks.com/ddr3-vs-ddr4/

[video="https://www.youtube.com/watch?v=utWnjA4NzSA"][/video]